Are Hb2 pencils for drawing?

I have hb2 pencils at home. People usually use it for writing in class. I'm wondering if hb2 pencils are for drawing. Are they? My portrait teacher says we should use 4h, 2h, hb, 2b, and 4b for doing our portraits. He didn't mention anything about an hb2 pencil. That's why i'm so curious!
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